As part of a BBC Radio 3 series marking the 450th anniversary of Shakespeare's birth five essayists are shedding light on the history and culture of the Midlands. In the second essay, writer and critic Henry Hitchings considers the importance of Erasmus Darwin - The Leonardo da Vinci of the Midlands.

Ask for a list of the innovations that changed Britain in the 18th Century and you will probably hear about the mechanical seed drill, the first efficient steam engines, the automation of weaving, the rise of factories, the growth of the canal network, and the expansion of print culture (which created fresh channels for circulating ideas). New attitudes accompanied these developments - a delight in the opportunities presented by commerce, an itch for political change.

What tends not to be acknowledged is how much of the period's innovation came out of the Midlands. It is no exaggeration to speak of a Midlands Enlightenment. But why did it happen there?

By the late 17th Century the Midlands, especially Birmingham, was home to vigorous communities of religious nonconformists - dissenting Christians, such as Quakers, who sought to evade the stifling grip of the Church of England. They were barred from attending the universities of Oxford and Cambridge: some pursued their studies at progressive institutions in Scotland, France or Holland, while others favoured local academies where the rich array of subjects might include geology, algebra and chemical experiments. Even though nonconformists were in a minority across the Midlands, they were highly visible, and the prevailing culture was one of free-thinking and social mobility, characterized by an unusual willingness to pool resources and share ideas.

There was no more important forum for this kind of intellectual exchange than the Lunar Society of Birmingham. Founded about 1765, this informal group, never more than 14 in number, took its name from the policy of holding its monthly meeting on the Monday afternoon closest to the full moon. The members, who in fact came from a wide range of religious backgrounds, referred to themselves as 'Lunarticks'. But there was nothing fanciful about their study of magnetism, ballistics, astronomy and education, all of which they explored in a spirit of optimism and friendship.

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Erasmus Darwin was the grandfather of Charles Darwin who laid the foundations of the theory of evolution

At the heart of the Lunar Society was a figure now not at all well-known: Erasmus Darwin. Say the name Darwin and people think immediately of Charles Darwin. But Charles's grandfather Erasmus was a figure perhaps even more remarkable - and he laid some of the ground for his more famous descendant's pioneering work on the origins and evolutionary development of life.

A polymath whose interests extended from mechanics to fungi, Erasmus Darwin was a speculative thinker of real daring - a crucial link between the eighteenth-century Enlightenment and the 19th Century's increasing embrace of industrial technology.

And he was a proud Midlander.

Born at Elston Hall near the Nottinghamshire market town of Newark, Erasmus Darwin was the seventh and last child of a lawyer. Darwin went to school in Chesterfield, and though his studies took him to Cambridge and Edinburgh, he returned to the Midlands for the rest of his life.

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Erasmus Darwin moved to Lichfield in November 1756

It was in November 1756, aged 25, that Darwin moved to Lichfield. The city was then the Midlands' cultural capital. For Darwin, who had previously faltered in his attempts to start a medical practice in Nottingham, Lichfield was a haven. He set himself up in a handsome Georgian townhouse near the city's stunning three-spired cathedral and - after saving the life of his first, supposedly doomed patient - quickly found professional success.

Although Darwin's reputation rests on achievements beyond medicine, to the people of Lichfield he was before all else a physician - and a boldly experimental one. He promoted treatments that were then unusual, taking a keen interest in exercise regimes and the benefits of good ventilation. He was sufficiently celebrated that he was approached to become the personal physician to King George III - an opportunity he declined.

But Darwin, who had studied both classics and mathematics at Cambridge, was never content to confine himself to a single discipline. While pursuing his medical career he dabbled in chemistry. He then drifted into the study of botany, cultivating an ornamental garden a mile from his house, which served as a test-bed for his theories about plant life. And like many of the key players in the Midlands Enlightenment, he fancied his chances as a businessman, planning an iron mill near Lichfield and teaming up with Wedgwood to promote the financial benefits of building canals.

He approached all of this with immense vigour. His unwieldy physique, limp and very large wig made his energetic activity - which also brought him 14 children - seem comical. In later years he found it necessary to have a section of his dining table cut away to allow room for his huge belly. We may smirk at that detail, but it is a mark of his pragmatism.

Darwin's great range of knowledge informed an astonishing variety of projects. After the death of his first wife Darwin had two daughters, Susan and Mary, with his son's governess, and this in due course prompted him to think carefully about the education of young women - not then a subject that exercised many men. Adamant that the daughters of the gentry should be educated in schools, rather than at home as was then normal, he advocated that they study languages and become financially literate. They should also have a clear grasp of manufacturing - especially the recent achievements of his friends from Birmingham's Lunar Society.

He also revelled in more humdrum concerns: pest control, ways of improving the quality of timber, the correct use of manure. He could hold forth about oil drilling, submarines and telescopes, and he foresaw the existence of both tower blocks and traffic jams. Yet his methods could sometimes seem bizarrely casual, as when he tried to cure a five-year-old's squint by fitting him with a giant false nose.

By the time Darwin died in 1802, his achievements had been obscured by suspicion. Other champions of the Midlands Enlightenment were riding high.

Yet Darwin was mainly a target for vicious satire, with attackers accusing him of atheism - he had chosen to worship not God, but Venus.

When Charles Darwin wrote a biography of his grandfather in the 1870s, he neglected to mention Erasmus's most provocative view: that all living things are descended from a single ancestor and have evolved over time. Erasmus Darwin was aware that this was sure to be a controversial idea, and kept quiet about it for a quarter of a century. When he chose to unleash it, his contemporaries were appalled. Indeed, one of the crucial respects in which he influenced his grandson Charles was in illustrating the perils of challenging orthodoxy. Charles recognised that if he was to change public understanding of man's place in the world, he should steer clear of thorny questions to do with politics and religion.

Erasmus Darwin had done the very opposite. "All nature exists in a state of perpetual improvement," he wrote, offending political and religious conservatives equally. He preached the Enlightenment gospel of progress, emphasizing the adaptive and inventive abilities of mankind. And in a typically confident and personal gesture, he chose to add to the family's coat of arms the Latin phrase 'E conchis omnia' - 'Everything from shells.'

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Some of Erasmus Darwin's designs were brought to life at his former home

If Erasmus Darwin is almost invisible to us now, it is partly because of Charles Darwin's fame and partly because Erasmus's critics went to such lengths to portray him as a crank. Yet to a modern eye Erasmus Darwin's capacity for innovation makes him one of the outstanding figures of the age. Some of his inventions were purely whimsical: a mechanical bird, and a metal spider that could be made to move around using a hidden magnet. Others, though, were of great practical use. He developed a steering mechanism for his carriage, which laid the basis for modern car steering, as well as a lift to help barges negotiate canals, a machine for duplicating documents, devices for monitoring the weather, and a horizontal windmill for Wedgwood - to grind the pigments used in producing his pottery.

Some of his most intriguing ideas never made it past his notebook: one was using hydrogen balloons to increase the amount that could be carried in wheelbarrows, another, a machine that could imitate the human voice, a third, an early version of the internal combustion engine.

We may think here of another inventor whose notebooks were packed with ingenious designs and tantalizing fragments of original wisdom: Leonardo da Vinci. No less inquisitive, and no less imaginative, Erasmus Darwin is the da Vinci of the Midlands.

The essay will be broadcast on BBC Radio 3 on Tuesday 22 April at 22:45 BST.